The present invention relates, in general, to water, superheated water and steam peelers for food products, and more particularly, relates to methods and apparatus for superheated water peeling of food products such as tomatoes.
Superheated steam peelers are in widespread for peeling tomatoes and other fruit, produce or food products. U.S. Pat. Nos. 6,056,987, 5,682,812, 4,707,372 and 4,101,682 are all directed to steam peelers for fruit or produce. U.S. Pat. Nos. 6,056,987 and 5,682,812 describe systems which are being commercially exploited by FMC Corporation to peel tomatoes, and such systems are also described in an FMC Corporation brochure entitled xe2x80x9cSP-20 Steam Peeler System.xe2x80x9d
In superheated tomato steam peeling systems, the pressure vessel employed is typically a drum that is slightly inclined so that condensing steam in the drum will drain away from the tomato discharge valve from the pressure vessel. A drum with internal auger or screw is provided in the pressure vessel to convey the tomatoes from one end of the pressure vessel to the upwardly inclined discharge end of the vessel, while steam condensate gravitates to the lower or inlet end of the pressure vessel. This allows the discharge valve at the upper end to receive steam treated fruit with loosened skins without also discharging condensate with the tomatoes. Once the tomatoes are discharged from the pressure vessel, they typically will be vacuum peeled. If significant condensate is also discharged with the tomatoes, vacuum peeling will produce inconsistent results as the condensate flashes under the negative pressure, rather than moisture under the loosened skins.
Peeling of produce, and particularly tomatoes, using superheated water has also been employed. A commercially exploited system has been introduced to the United States which is sold by FMC Corporation under the trademark SATURNO. A brochure distributed by FMC Corporation de scribing this system is entitled xe2x80x9cFMC Food Tech-Tomato Peeling Systemxe2x80x9d and is incorporated herein by reference. In the SATURNO peeler system, superheated water is used, rather than superheated steam, because it increases heat transfer to the produce to enable greater peeling efficiency and allow higher throughputs.
In the SATURNO system, however, two ferris wheel-type drums are employed in the pressure vessel. A first carries the tomatoes down into the superheated water and then transfers them into a second compartment. The second ferris wheel-type drum raises the tomatoes into an upper steam portion of the pressure vessel for final heating and discharge at a position above the water level.
Hot water at atmospheric pressure also has been employed to loosen the skins of tomatoes for peeling. Existing hot water peelers, however, operate at temperatures of up to only 212xc2x0 F. After heating in the water, the tomatoes, which are not in a pressure vessel, are removed from the water into a discharge valve and exposed to steam at elevated pressure for a short period of time while in the discharge valve. The tomatoes are then peeled using a vacuum. Because of the limited time in which the skins can be exposed to pressurized conditions, hot water peeling encounters efficiency and throughput difficulties, particularly in connection with peeling late maturing varieties of tomatoes.
The use of pressurized superheated water peelers overcomes the problems of atmospheric hot water peelers in that the food product is immersed or submerged in water which typically has a temperature of about 235-240xc2x0 F., but may have a temperature as high as 270xc2x0 F. Superheated water contact results in higher peeling efficiency and better yield, but the problem of separating the food product from the superheated water in a pressure vessel have been substantial. Attempts have been made, for example, to adapt the SP-20 superheated steam peeler to one in which superheated water is used, but once the water level in the pressure drum reaches the discharge valve, discharge of superheated water from the pressure vessel impairs vacuum peeling. If the SP-20 superheated steam peeler is filled with superheated water to a level just below the discharge valve, the volume of superheated water will not be sufficient to fully submerge most of the food product, and peeling efficiency is only slightly better if the apparatus is operated as a steam peeler.
The apparatus for removing skins from a food product having skins, such as a tomato, of the present invention comprises, briefly, a pressure vessel formed to contain a volume of water in a superheated state for immersion of a volume of fruit into the water; a discharge valve positioned for receipt and discharge of superheated water and fruit together from the pressure vessel to the valve. The discharge valve is further formed for separation of the superheated water from the food product for discharge of the food product apart from the water into a skin removal device. The skin removal device receives discharged, separated food product from the discharge valve of the present invention, and most preferably but not necessarily, the skin removal device is provided as a rotary valve formed to progressively expose the food product to superheated steam and thereafter vacuum. Further peeling by cable peelers or rubber cord scrubbers, pinch rollers and the like also can be provided.
In the preferred form, the present discharge valve also is a rotary valve which moves the food product from a station at which the valve receives the food product in the superheated water to a station at which the water is separated, preferably by employing a slight pressure difference between the discharge valve and a water-receiving reservoir, as well as gravitation of the water away from the food product while the food product is supported in the valve. Finally, the valve moves the food product to a discharge station at which the food product is discharged from the valve into the peeling device. The separated superheated water can be heated, filtered and then pumped back into the pressure vessel.
The present invention also includes a discharge valve which can be retrofit to existing superheated steam peelers so as to enable their conversion to superheated water peelers. Thus, the present discharge valve comprises, a valve body formed for positioning relative to a pressure vessel for receipt of superheated water and food product therefrom. The valve is formed for separation of the water from the food product while the food product is contained in the valve and is formed to thereafter discharge the separated food product from the valve for subsequent peeling, for example, for vacuum peeling. A pocketed rotary valve having a separation station formed with a perforated wall for discharged water from the pockets while the food product remains in the pockets is particularly well suited for this purpose.
In a final aspect of the present invention, a method of removing skins from a food product is provided which includes the steps of immersing the food product having skins in a volume of superheated water in a pressure vessel for a time sufficient to loosen skins; removing the food product with loosened skins and a portion of the superheated water from the pressure vessel; thereafter, separating the food product and the superheated water; and after the separating step, removing the skins from the food product. The removing step may be accomplished by applying steam to increase pressure in the skin removal device and then applying a vacuum to separate or flash the loosened skins from the food product.